1. Field of the Invention.
The present invention relates to a hydraulic lifting system for raising and lowering a movable top that covers a hole through a primary roof structure. In this case, the primary roof structure relates to a van used for camping purposes; however, the same system may be used with camping trailers, buses or any other structure in which it may be desirable to increase the head room.
2. Description of the Prior Art.
It is a well known practice to design recreational vehicles, campers, travel and camper-type trailers and car top mounted sleeping quarters as small and as compact as possible, to provide reduced wind resistance, lower the center of gravity and increase visibility so they may be more easily and safely driven or towed on the road. Then, of course, it is necessary to provide a means for expanding the structures to provide adequate room. It is very desirable to obtain increased head room so that most people may move about the living areas in a fully erect posture. For example, the use of kitchen, living areas and toilet facilities is much more comfortable with adequate head room.
One such device is disclosed in U.S. Pat. No. 3,286,414, issued to C. J. Harrison, et al. This patent teaches a camper body in which the camper top is raised by hydraulic or screw jacks located at the four corners of the camper body. The jacks are attached directly to the moveable roof without the use of a linkage system. No system is disclosed for operating the hydraulic or screw jacks.
U.S. Pat. No. 3,489,452 to V. Plante discloses a camper trailer which utilizes one set of hydraulic cylinders and attached linkages to raise the camper's tent like structure and another set to collapse it. In FIG. 9, the patent discloses the use of a double acting hydraulic cylinder and a lazy tong linkage system as an alternate means for opening and closing the camper.
U.S. Pat. No. 4,366,979 to B. Pillot discloses an expandable roof top camper that utilizes articulated arms located at each of the four corners of the camper. The articulated arms are pushed into an open position by jacks operated by either a spring, air pressure or hydraulic fluid. The hydraulic jack is a single acting self-contained system with no separate hydraulic system disclosed.
U.S. Pat. No. 3,575,460, issued to W. Kennedy discloses a portable sleeping mechanism mounted to the roof of a vehicle which is raised or lowered by a linkage system. The linkage system provides simultaneous lateral and vertical movement and may be operated by a double acting hydraulic piston.
U.S. Pat. No. 4,103,958, issued to J. Parent discloses a camping vehicle, in particular a bus body having a roof detachable from the main body of the bus structure. The roof is raised by hydraulic cylinders to provide a second floor sleeping area. The roof is elevated by hydraulic cylinders. Pairs of these cylinders are joined together by an intercoupling system to provide a concerted action between the coupled cylinders.
The jack systems utilized by Harrison and Parent are inefficient as a means for lifting a roof section as opposed to an entire roof, since the jacks would intrude into and restrict the useable living space. Articulated arms as disclosed by Pillot are not compact and will also be intrusive as they do not fold completely flat. The lever system of Kennedy provides simultaneous vertical and lateral movement; lateral movement is detrimental when raising a roof section where it is much more efficient to lift in a vertical direction only. The more lateral movement permitted the more wasted space that will result.
The current invention provides an efficient means for raising and lowering an expandable top that covers a hole constructed through the hardtops of vans, recreational vehicles, campers, camper trailers or other similar vehicles. The current invention uses a push/pull system operated by double ended, double acting hydraulic cylinders that, in conjunction with a compact scissor lifting mechanism, eliminates bulky and intrusive jack and lever systems, provides a simple intercoupling system for pairs of lifting mechanisms and provides an almost vertical lifting action. In addition, the invention provides a locking mechanism to ensure safety by positively retaining the expandable top in its lowered position.